Blood flow (BF) is the movement of blood through the vessels of the circulatory system. The right and left sides of the heart work together. The pattern described below is repeated over and over again, allowing blood to flow continuously through the heart, lungs, and body.
How Does Blood Flow Through Your Lungs?
Once blood travels through the pulmonic valve, it enters your lungs. This is called pulmonary circulation. From your pulmonic valve, blood travels to the pulmonary arteries and eventually to the small capillary vessels in the lungs. Here, oxygen moves from the small air sacs in the lungs, through the walls of the capillaries, into the blood. At the same time, carbon dioxide, a waste product of metabolism, passes from the blood into the air sacs. When you exhale, carbon dioxide is expelled from the body. Once the blood is oxygenated, it moves back to the left atrium via the pulmonary veins.
Blood Flow Step by Step
The heart consists of two upper chambers—the left and right atrium—and two larger lower chambers—the left and right ventricles. A series of valves control the flow of blood in and out of these chambers. Electrical impulses, controlled by the cardiac conduction system, cause the heart muscle to contract and relax, creating the rate and rhythm of your heartbeat. Here are the stages of blood flow through the heart and lungs:
Blood first enters the right atrium.
Blood then flows through the tricuspid valve into the right ventricle.
When the heart beats, the ventricle pushes blood through the pulmonary valve into the pulmonary artery.
The pulmonary artery carries blood to the lungs where it “picks up” the oxygen and then leaves the lungs to return to the heart via the pulmonary vein.
Blood enters the left atrium, then descends through the mitral valve into the left ventricle.
The left ventricle then pumps blood into the aortic valve and the aorta, the artery that feeds the rest of the body, through a system of blood vessels.
Blood returns from the body to the heart through two large blood vessels called the superior vena cava and the inferior vena cava. This blood carries little oxygen, as it is returning from the body where the oxygen was used up.
The vena cavus pumps the blood into the right atrium and the cycle of oxygen and transport begins all over again.
